Commentaries of the Four Authorized Vaisnava Sampradayas

Here Lord Krishna is emphasising the importance of the mind regarding yoga
or the science of the individual consciousness attaining communion with the
ultimate consciousness. For one whose mind is uncontrolled it is not
possible to practice yoga but that person who has controlled their mind by
dispassion and regular practice and meditation can succeed in yoga by
striving repeatedly.

Brahma Vaisnava Sampradaya:

Madhvacarya

Madhvacarya's Commentary

It should not be thought that the mind of its own accord becomes controlled
because that is not the case. For those who are unrighteous, who do not
desire what is good for other created beings, who hate, who are debauchers,
who are non-believers of the Vedic scriptures and other such persons, the
opportunity for moksa or liberation from the endless cycle of birth and
death in the material existence never manifests. This has been
categorically confirmed in the Brahma Purana.

Sri Vaisnava Sampradaya:

Ramanuja

Ramanuja's Commentary

That the mind is difficult to control and direct due to its fickle and
tempestuous nature is a fact unable to deny. But the possibility of taming
it depends upon generating in the mind a feeling of affection and
attachment by accustoming the mind to regularly reflect on the sublime,
transcendental qualities of the atma or soul and then meditating upon the
atma daily. In this way very soon an aversion will arise to focus on
anything that does not facilitate atma tattva or realisation of the soul.
This will happen naturally when the discerning mind perceives the
imperfections inherent in all other topics and subjects. Lord Krishna is
reiterating that for one who has not subjugated their mind this yoga or the
science of the individual consciousness attaining communion with the
ultimate consciousness by dhyana or meditation is extremely difficult to
realise; but it is possible to achieve by one who has the vision of
equanimity towards all beings and understands that the same fundamental
spiritual basis is present everywhere as the atma existing in all living
entities. Controlling the mind has already been elucidated by Lord Krishna
in the process of selfless karma yoga as offerings of worship to the
Supreme Lord. Lord Krishna has also instructed in chapter II.XXXX that
there is no loss or diminution by the performance of this yoga; but the
greatness of karma yoga there described is certainly that which embodies
atma tattva and culminates in communion with paramatma the Supreme Soul by
meditation.

Kumara Vaisnava Sampradaya:

Nimbaditya

Kesava Kasmiri's Commentary

Lord Krishna is confirming that it is not possible to become established in
yoga or the science of the individual consciousness attaining communion
with the ultimate consciousness by dhyana or meditation. To behold all with
equanimity and dispassion is not possible for one whose mind is restless
and uncontrolled. But through ceaseless striving and constantly practising
of meditation it is possible to be successful in controlling it.